Nikon F90x autofocus settings?

[dugrant153]

Hey all,

So I did a few assignments with my Nikon F90x and surprisingly... a lot of shots are out of focus. I'm using a manual focus 50mm F1.4 Ai lens so I use the electronic rangefinder and rely on it quite heavily since I shoot in lower light.

The thing is, I used it in spot AF mode (vs wide AF mode) most of the time and am wondering if this is potentially the cause of my AF woes? Or has anyone else experienced F90x's suffering from back/front focusing (even on the electronic rangefinder and manual focusing?).

Thanks!

[mgb74]

Did you perhaps lock in the AF by partially depressing the shutter release before final composition?

[markbarendt]

My N90s does well focussing that way.

[dugrant153]

Did you perhaps lock in the AF by partially depressing the shutter release before final composition?

My lenses are manual focus only so don't think this would affect it? I just tried it and seems that the electronic rangefinder is independent of depressing the shutter slightly.

My N90s does well focussing that way.

Do you mean spot focusing? or wide-area?

[markbarendt]

Spot normally, but actually either.

[PhotoJim]

1. Test by tripod-mounting your camera and running some test images. Focus very, very carefully. Try other test shots with the focus intentionally shifted a little back and forward (and note which are which) and see what you get for results.

2. Check the focusing screen above the mirror, at the bottom of the pentaprism. If the screen holder isn't properly secured, you won't attain proper focus.

[dugrant153]

So after getting some film back, I realize it may not actually be the camera... but the 50mm lens. There was definitely a lot of decentering going on as I'd have the first half of the image in focus and then the other half starting to fade. Pretty nasty.

Thanks for all the tips. I remedied this problem by buying a new 50mm lens.

[markbarendt]

I don't understand what you mean by de-centering.

Do you mean foreground in and background out?

What aperture was used?

How far from the subject were you?

[dugrant153]

By decentering, I mean that the image is in focus for about 60% across the image but the rest suddenly just blurs up. In my case, the far right side (when horizontal) of the image was blurring up while the rest of the image was in focus. I thought this was just a depth of field thing but even some objects that were in the correct plane of focus were blurring up. That is, some of the objects would be in focus and suddenly the rest... well, it goes to pot.

Great for tilty-shifty stuff, but not for what I was looking for!

[markbarendt]

By decentering, I mean that the image is in focus for about 60% across the image but the rest suddenly just blurs up. In my case, the far right side (when horizontal) of the image was blurring up while the rest of the image was in focus. I thought this was just a depth of field thing but even some objects that were in the correct plane of focus were blurring up. That is, some of the objects would be in focus and suddenly the rest... well, it goes to pot.

Great for tilty-shifty stuff, but not for what I was looking for!

Couple thoughts.

1 If it is always the right side on the film, the pressure plate that holds the film may have a bad spring, or something of that nature that is keeping the film from laying flat. Given your description this seems very probable. If true this also nearly rules out viewfinder/focusing screen issues.

2 If your subjects are close and aperture wide, your plane of focus may be measured in mm. If this is the issue in good light it will be reasonably easy to see the effect in the viewfinder. At 1.4 it isn't to tough to get a plane of focus that is say 10mm or less deep.